More than 800 Android apps in the Google Play Store were infected with malware that quietly stole personal and financial data from users. Xavier, a form of Trojan adware, hid inside several types of apps - call recorder, photo manipulator, ringtone changers and more.

According to intelligence security firm Trend Micro on Tuesday, the malicious software has been downloaded millions of times across the globe.

"Xavier...has the capability to download and execute other malicious codes, which might be an even more dangerous aspect of the malware," the Tokyo-based company said. "Xavier’s stealing and leaking capabilities are difficult to detect because of a self-protect mechanism that allows it to escape both static and dynamic analysis."

Xavier was downloaded in Vietnam, the Philippines, Indonesia, the U.S. and Europe.

The apps have been removed from the Google Play Store. A full list of infected applications can be found here.

Android smartphone owners should avoid downloading and installing apps from unknown sources, even if they're featured in the Google Play Store. Reading user reviews is also helpful - apps that show suspicious behavior will often have low ratings.